Electron Spin Resonance Spectral Studies Research Articles

Electron spin resonance spectral studies of the metal complexes formed in the solvent extraction systems—vanadyl complexes with long-chain alkyl amine and alkyl ammonium compound

Electron spin resonance spectral studies have been carried out on complexes formed in the extraction of vanadium(IV) from hydrochloric acid solutions by tri- n-octylamine (TOA) and tricaprylmethylammonium chloride (R 3R′NCl) in benzene. The spectra are analyzed assuming the axial symmetry, magnetic hyperfine interaction and Lorentzian line shape. Values of resonance parameters determined for the vanadyl complexes with TOA are g || = 1.947, g ⊥ = 1.981, | A| = 0.0128 cm −1 and | B| = 0.0054 cm −1 and with R 3R′NCl, g || = 1.948, g ⊥ = 1.980, | A| = 0.0140 cm −1 and | B| = 0.0055 cm −1. Spectroscopic, molecular weight and magnetic studies indicate that the vanadyl complexes have distorted octahedral structures of compositions [R 3NHVO(OH)Cl 2] 2 and [R 3R′NVO(OH)Cl 2] 2, respectively.

Electron spin resonance spectral studies of the metal complexes formed in the solvent extraction systems Divalent manganese and copper complexes with di-(2-ethylhexyl)-phosphoric acid

The complexes formed in the extraction of divalent manganese and copper from hydrochloric acid solutions by di-(2-ethylhexyl)-phosphoric acid (DEHPA;HX) have been investigated by electron spin resonance (ESR) spectroscopy. On the basis of the results, the g-values and hyperfine splitting constants for the DEHPA-complexes are determined by computer simulation; manganese(II), g = 1.996 and |Aav| = 0.00718 cm−1; copper(II), g= 2.333, g⊥ = 2.076, |A| = 0.00786 cm−1 and |B| = 0.00078 cm−1. Spectrophotometry and magnetic studies show that the monomeric species Mn(X2H)2 and Cu(X2H)2, which are tetrahedral and square planar, respectively, are formed in the organic phase when DEHPA is present in excess. It is deduced for the copper complex that in-plane σ-bonding is appreciably covalent and that in-plane and out-of-plane π-bonding are ionic.

High Spin and Low Spin Forms of Co(II) Carbonic Anhydrase: TEMPERATURE-DEPENDENT CHANGES IN SPIN STATE AND COORDINATION GEOMETRY

Abstract Electron spin resonance (ESR) and absorption spectral studies are described which demonstrate two types of cyanide complex of Co(II) human carbonic anhydrase B. High spin (S = 3/2) Co(II) is present at the active site of the cobalt enzyme in the presence of both 1 and 2 eq of CN- at room temperature. At liquid nitrogen temperature the 1:1 complex remains high spin, while the enzyme in the presence of 2 eq of CN- shifts to low spin (S = 1/2). ESR spectra at 111°K and 10°K and absorption spectra at 299°K and 77°K are compatible with tetrahedral coordination geometry for the 1:1 complex at all temperatures and for the enzyme in the presence of 2 eq of CN- at room temperature. Determination of the temperature dependence of the ESR and absorption spectra of the enzyme in the presence of 2 eq of CN- shows a low spin dicyanide complex to form when the sample freezes (∼273°K). The ESR spectra at liquid nitrogen temperature of the dicyanide complex formed with 12C14N-, 12C15N-, and 13C14N- show it to contain two ligands along the z-axis of the complex, a nitrogen atom from the protein and the carbon atom of a C-coordinated cyanide. A coordination complex consisting of a distorted trigonal bipyramid with five ligands to the Co(II) or an octahedral complex with six ligands would account for the ESR and absorption spectra of the low spin dicyanide complex at liquid nitrogen temperature. These changes illustrate a certain flexibility of the ligands at the active site as well as a difference in molecular conformation between the liquid and the frozen state.

Electron paramagnetic resonance spectral study of intramolecular reactions of aryl radicals

Electron paramagnetic resonance spectral study of intramolecular reactions of aryl radicals

A STUDY BY ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY OF RADICALS FORMED FROM ACETAMIDE AND FORMAMIDE

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Separation and Investigation of a Stable Solid Free Radical of Chlorpromazine

A solid stable free radical of chlorpromazine was prepared and characterized. The free radical nature of this compound was verified by electron spin resonance and ultraviolet spectral studies. The molecular weight and melting point of the free radical were determined. A solid stable free radical of chlorpromazine was prepared and characterized. The free radical nature of this compound was verified by electron spin resonance and ultraviolet spectral studies. The molecular weight and melting point of the free radical were determined.